This is to ensure that our sync logic for reading lists behaves the same for temporary accounts as it does for logged-out users. In other words, we should only synchronize the user's reading lists if they are logged in as a permanent account.

The rationale being that syncing of reading lists is for the purpose of accessing your lists from different devices, whereas a temporary account by definition cannot be accessed from anywhere else, and any synced lists will be a waste of space and bandwidth.

We may also modify the ReadingLists extension itself to return an error if attempting to sync lists to a temporary account, but we should simply prevent syncing from the client side regardless.